Pistons



Dec. 26, 1961 w. M. NICHOLS PISTONS Filed May 21, 1958 FlG.6

INVENTOR.

WILLIAM M- NIC HOLS ATTORNEY United Stats 3,014,771 PISTONS William M.Nichols, Schenectady, N.Y., assignor to Alco Products, Incorporated, NewYork, N.Y., a corporation of New York Filed May 21, 1958, Ser. No.736,789 Claims. (Cl. 309-14) This invention relates to pistons forinternal combustion engines and particularly to heavy duty diesel enginepistons of the class in which a piston body of light alloy is equippedwith a ring carrying insert of heavy wear resistant material such asiron.

A serious problem arises in the case of light bodyheavy ring insertcombinations in a piston because of the disparity of thermal expansionbetween the aluminum of the piston body and the ferrous alloy of thecarrier. As a result of such unequal expansion, the piston ring carrierswork loose and damage is caused to the piston and cylinders. Nickel orthe like has been added to the ferrous alloy of the insert so that itscoeflicient of thermal expansion will match or closely match thecoefiicient of the piston aluminum alloy. But, even with such anexpedient, it has been found that there is still a difference in thethermal coeflicients to cause minute upsetting of the aluminum alloy ofthe base when it grows against the restraining ferrous hand during theheating cycle. Such upsetting results in a looseness of the insert inrelation to the piston body.

Molecular bonding of the ferrous alloy insert to the aluminum alloypiston has also been tried as a solution to the problem. This has beenaccomplished by coating the insert with a thin film of molten aluminumoverlying a ferro-aluminum alloy layer at the interface and then, whilethe surface film is maintained at a temperature sufiicient to keep itmolten or plastic, placing the carrier in a permanent mold and castingthe aluminum alloy body around it. A fusion union is thus createdbetween the plastic film on the insert and the molten casting metal; andit has been found that a union so formed is strong enough to hold theparts in proper relation during engine operation. The piston bodyhowever, is thus limited to a casting and castings have disadvantageouscharacteristics on heavy duty operations.

The principal object of the invention, therefore, is to provide a pistonfor an internal combustion engine hav ing a body of light material suchas an aluminum alloy, and an insert which includes a durable wearresistant material such as a ferrous alloy, the combination having anovel arrangement such that the insert will not work loose from the bodyunder operating conditions. An-

other object is to provide such a piston which will have a body of analuminum or light alloy and an insert which includes a durable wearresistant material formed as a weld deposited in an annular receivinggroove in the piston body. Another object is to provide such a pistonwhich includes an insert in the form of a weld which has a matrix of analuminum alloy molecularly bonded to the aluminum alloy of the pistonbody, the weld having particles of iron or the like dispersed throughoutthe matrix to provide it with desired wearability. Another object is toprovide such a piston having a body of an aluminum or light alloy and aring insert formed as a weld deposited in an annular receiving groove inthe piston body, the weld consisting of a composition having a matrix ofthe same alloy as contained in the piston body and ferrous alloy orother wear resistant particles dispersed throughout the matrix toprovide the composition with desired hardness and wearability.

In the drawings, FIG. 1 shows a portion of a piston having a pluralityof ring grooves, the top groove being formed in the periphery of aninsert deposited as a weld Patented Dec. 26 196i in an annular recess inthe piston body. In FIG, 2 the piston is of the oil cooled type with aband shrunk on to the piston body, the ring grooves being formed in theband and the top groove being located in an insert in the form of aweld. In FIGS. 3, 4, 5, and 6, the steps in the formation of the topgroove are illustrated; FIG. 3 showing the portion of the piston withthe weld recess formed therein, FIG. 5 showing the weld deposit machined0E flush with the outer wall of the piston, and FIG. 6 showing the weldwith the ring groove machined therein.

Referring now to the drawings, numeral 10 indicates the body of a pistonof an internal combustion engine; It is of a light alloy composition,such as an aluminum alloy. Conventional ring grooves 11 are formed inthe body wall for the reception of compression rings of a heavy durablematerial such as a ferrous alloy. Such combinations of a light alloypiston body and a heavy durable compression ring are well known in thediesel engine field. As here illustrated, piston body 10 is providedwith a recess 12 adjacent its top face. Within recess 12 a weld isdeposited thus forming insert 13 having particles 14 of a Wear resistantmetal dispersed therein, such particles 14 providing a wearing surfacefor top I ring groove 15 machined in insert 13. The weld may bedeposited by gas welding or by electric arc welding with a filler rodhaving a matrix of an alloy that will bond securely to the material ofthe body. In the case of an aluminum alloy piston, the rod matrix isa'related aluminum alloy. Mixed into the matrix is even dispersion areparticles 14 of a hard durable material such as a ferrous alloy. Desireddurability is imparted to the weld by the ferrous or other suitableparticles. The machining of the groove 15 into the weld can be done byconventional means.

In FIG. 2 the piston is of the oil cooled type in which a passage 16transmits cooling oil through the piston body from the lubricatingsystem of the engine. For convenience in manufacture, the piston body 10is fabricated with an annular recess 17 at its upper end with the oilcooling passage 16 open at the peripheral surface of the body. Anannular band 10a is shrunk on to the body to close the oil passage. Inthe construction shown, the band 10a is slotted adjacent its top face sothat the top cooling passage 18 is located closer to vertical alignmentwith the ring grooves for more effective cooling. In such a constructionthe piston body may be cast or forged and the band may be forged.

The term piston body or body portion is intended to include not onlybody 10 as illustrated in FIG. 1 but also body 10 and band 10a asillustrated in FIG. 2.

While there has been hereinbefore described an approved embodiment ofthis invention, it will be understood that many and various changes andmodifications may be made without departing from the spirit of theinvention, and that all such changes and modifications as fall withinthescope of the appended claims are contemplated as a part of thisinvention.

What I claim is:

1. A piston for an internal combustion engine comprising a cylindricalbody portion of a light metal alloy of relatively low strength, saidbody portion having an annular recess adjacent its top face; a weld inthe recess having a matrix of an alloy bondable to the alloy of the bodyportion and particles of a heavier metal alloy dispersed throughout thematrix; and recess means in the periphery of the weld adapted to carry acompression ring.

2. A piston for an internal combustion engine comprising a cylindricalbody portion of an aluminum alloy, said body portion having an annularrecess adjacent its top face; a weld in said recess, said weld having amatrix of aluminum. alloy and particles of ferrous alloy dispersedthroughout the matrix, and recess means inthe periphery of the weldadapted to carry a compression ring. I

3. A piston for an internal combustion engine comprising a cylindricalbody portion of a relatively low strength light metal alloy of the classconsisting of alumimum and aluminum alloys, said body having an annularrecess adjacent its top face; a weld in said recess, said weld having amatrix of light metal of the class consisting of aluminum and aluminumalloys and particles of ferrous alloy dispersed throughout the matrix;and recess means in the periphery of the Weld adapted to carry acompression ring.

4. A piston, according to claim. 3, in which the ferrous alloy particlescomprise substantially 25 of the surface of the recess means.

5. A ring carrier for a piston comprising a band 4? band and particlesof a heavier metal alloy dispersed throughout the matrix, and recessmeans in the periphery of the Weld adapted to carry a compression ring.

References Cited in the tile of this patent UNITED STATES PATENTS2,818,841 Nichols Jan. 7, 1958 OTHER REFERENCES Diesel Power, vol. No.33, Issue No. 4 pages 54-55,

adapted to be secured to the upper portion of a piston, bli April 1955an annular groove in said band, a weld in the groove having a matrix ofan alloy bondable to the alloy of the

